1922] ,119 



YOUNG — THE TOXIC PROPERTY OF SULPHUR 4 Id' 



solution was formed. Hydrogen sulphide was then passed into 

 the sulphurous acid solution, care being taken not to have an 

 excess of the hydrogen sulphide, as it precipitates the hydrophilic 

 colloidal sulphur forming the hydrophobic colloid. The solu- 

 tion was then centrifuged to remove the larger particles and the 

 supernatant liquid coagulated with sodium chloride. The coag- 

 ulum was then peptized in water as before. 



The hydrophobic colloidal sulphur can be prepared in a num- 

 ber of ways. It is the "milk of sulphur" formed when sulphur 

 is precipitated out of solution. It was prepared in this work by 

 the method used by v. Weimarn and Molyschew (11) which 

 was as follows: Sulphur was recrystallized in toluol and the 

 toluol evaporated off at 60-70° C. Five-tenths gm. of this was 

 heated with 125 cc. of fresh distilled absolute alcohol in a reflux 

 condenser for 60 minutes. Seven cc. of this hot solution were 

 poured into 293 cc. of distilled water at room temperature. The 

 suspension prepared in this way was white and turbid. This was 

 centrifuged and resuspended in water. The sulphur particles 

 settled out of this suspension in a comparatively short time. 



In determining the toxicity of these forms of colloidal sulphur 

 the same method was used as in the preceding tests. With the 

 hydrophilic colloidal sulphur, however, it was necessary to make 

 a much weaker suspension. The stock colloidal suspensions con- 

 tained about 1.5 per cent sulphur. Five cc. of this stock sus- 

 pension were diluted to 25 cc. with distilled water, and then 1 

 cc. of this was added to each of the hydrogen-ion concentrations. 

 This gave a further dilution of 1 : 5 and resulted in a very weak 

 suspension of colloidal sulphur. After a preliminary test, how- 

 ever, the hydrophobic colloidal sulphurs were not diluted with 

 water, and 1 cc. of the stock suspension was added directly to 

 the culture solutions. The organisms used and the results are 

 recorded in table i and figs. 1-4. 



With the 6 organisms used in this experiment hydrophilic 

 colloidal sulphur was found to be extremely toxic in the very 

 dilute suspensions used. Only 2 of the organisms, namely, Bo- 

 trytis cinerea and Macrosporium sarcinaeforme, showed a slight 

 resistance to this suspension. In stronger suspensions germina- 

 tion was entirely inhibited with all the organisms used. On the 

 other hand, hydrophobic colloidal sulphur was only slightly toxic 

 and comparable to ground flowers of sulphur. The results in- 

 dicate that sulphur is most toxic in a very finely divided state 



